Virić Gašparić et al.: Impact of environment on ground beetles populations - 697 - IMPACT OF ENVIRONMENTAL CONDITIONS AND AGRO- TECHNICAL FACTORS ON GROUND BEETLE POPULATIONS IN ARABLE CROPS VIRIĆ GAŠPARIĆ, H. ‒ DRMIĆ, Z. ‒ ČAČIJA, M. ‒ GRAŠA, Z. ‒ PETRAK, I. ‒ BAŽOK, R. ‒ LEMIC, D.* University of Zagreb Faculty of Agriculture, Department of Agricultural Zoology, Svetošimunska 25, 10000 Zagreb, Croatia (phone: +385-1-2393-804) *Corresponding author e-mail: [email protected] (Received 15th Nov 2016; accepted 7th Mar 2017) Abstract. Ground beetles (Coleoptera: Carabidae) are the largest family of adephagan beetles. Their role in natural pest control is important due to their predatory polyphagous nutrition and bioindicative value since they are sensitive to environmental and anthropogenic changes. Therefore, the main objectives were to understand how common arable cropping systems in Croatia affect ground beetles abundance in respect to the environmental conditions. We hypothesized that environmental specifics (soil type and structure, climatic conditions) together with cultivation measures (tillage and insecticide application) would affect ground beetle activity and abundance. The research was conducted in two locations Lukač, Virovitica – Podravina County and Tovarnik, Vukovar – Sirmium County. Ground beetles were collected weekly, from May to September 2015, by epigeic pitfall traps and endogeic perforated probes from fields sown with typical arable crops in these areas. In total, 2,582 ground beetle individuals were collected using epigeic traps, and 323 ground beetles were collected using endogeic traps. Significantly lower ground beetle abundance has been recorded in Tovarnik than in Lukač. The crop and cropping history affect the abundance through modification of environmental conditions (soil characteristics, microclimate factors such as temperature and humidity), as well as trough disturbance factors such as tillage schedules and harvest/sowing schedules. Keywords: carabids, agro-technical measures, environment, plant cover, abundance Introduction Ground beetles (Coleoptera: Carabidae) with over 40,000 species are the largest family of adephagan beetles (Lövei and Sunderland, 1996) inhabiting arable crops all over the world (Kromp, 1999). They are often used in cultivation experiments because they are one of the most abundant and diverse groups overwintering within cultivated fields (Holland and Reynolds, 2003). Ground beetles are bioindicators of agroecosystems quality (Cole et al., 2002; O´Rourke et al., 2008) and can be good ecological indicators of environmental change (Thiele, 1977; Maelfait, 1990). In term of environmental quality, arable land presents an anthropogenically influenced, unstable and devastated biotope with low contribution to farmland diversity (Baranová et al., 2013). Environmental change can cause a different kind of effects on the indicator species, including physiological changes or changes in species number and abundance (Raino and Niemelä, 2003). Increase or decrease of ground beetle abundance might be directly caused by the change in many abiotic and/or biotic factors (Blake et al., 1996). These factors include temperature and humidity (Lövei and Sunderland, 1996), soil characteristics, land heterogeneity and agricultural measures such as tillage, crop type, APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 15(3): 697-711. http://www.aloki.hu ● ISSN 1589 1623 (Print) ● ISSN 1785 0037 (Online) DOI: http://dx.doi.org/10.15666/aeer/1503_697711 2017, ALÖKI Kft., Budapest, Hungary Virić Gašparić et al.: Impact of environment on ground beetles populations - 698 - fertilization regimes, crop rotation and pest control (Stassart and Grégoire-Wibo, 1983; Kromp 1999; O´Rourke et al., 2008; Kos, 2010; Asteraki et al., 1992; 1995). A further decisive factor for habitat selection considering soil specifics is soil particle size distribution (Thiele, 1977; Meissner, 1984). Vician et al. (2015) stated that content of organic matter and pH are the most significant factors that influence ground beetle diversity and abundance in agroecosystems. Some aspects of landscape heterogeneity (e.i. field size (Kromp, 1999), non-cropped habitat (Pollard, 1968; Sotherton, 1985) and land use diversity (Östman et al., 2001)), will also influence the ground beetles communities (Chapman, 2014). Stassart and Grégoire-Wibo (1983) stated that depth of tillage is one of the major factors affecting ground beetle field fauna. Dobrovolsky (1970) and Baguette and Hence (1997) reported that deep cultivation had a detrimental effect on ground beetle abundance. Opposite to that, Cárcamo (1995) and Weibull et al. (2003) trapped significantly more ground beetle individuals under intensive tillage compared with reduces tillage. Arable crops can affect ground beetles through modification of microclimatic factors, and trough disturbance factors (harvest and tillage schedules; Thiele, 1977; Witmer et al., 2003; O´Rourke et al., 2008). Although no ground beetles appear to be strictly related to certain crops, some studies reported a general difference between ground beetle abundance distributions in winter cereal versus root crops (beets) (Kromp, 1999). In root crops, the long period of bare soil in early spring present extreme soil-surface microclimate which has a negative influence on ground beetle abundance. In winter cereals, the less extreme microclimate is established in early spring and creates positive conditions for many ground beetle species (Kromp, 1999). Also, ground beetle abundance can be influenced by the crop-dependent timing of cultivation measures. Spring tillage and insecticide treatments can affect ground beetles at the beginning of their activity, but also, autumn tillage and insecticide treatments can disturb ground beetles overwintering (Hence et al., 1990). However, the effects of soil tillage could not be clearly separated from the effects of different fertilization regimes (e.g. manure, mineral fertilizers) and may also vary with the crop, and among localities. Pietraszko and De Clercq (1982) and Hence and Grégoire-Wibo (1987) revealed organically manured fields to have higher ground beetle diversity and abundances. Similar results were reported by Bažok et al. (2007) and by Kos et al. (2011) in Croatian conditions. Kromp (1990) showed that the ground beetle abundance and diversity significantly decreased in the fields with the high amount of nitrogen applied as mineral fertilizer, manure and liquid manure. The population of ground beetles in the agricultural landscape can be also influenced by the chemical pest control (Varvara et al., 2012). Basedow (1987) investigated ground beetle populations in winter wheat fields and found a significant decrease of ground beetles density as a consequence of intensive insecticide application against cereal aphids. Opposite results were established by Kos et al. (2010) who did not find significant differences in ground beetle abundance between treated and untreated fields. Negative effects of insecticides on ground beetles were recorded by Asteraki et al. (1992; 1995). Douglas et al. (2014) shown that insecticides (e.g. thiametoxam) can be poisonous to ground beetles due to their predatory nature. This means that chemical treatment of some agricultural pests can also affect ground beetles that consumed them (Jeschke et al., 2011; Szczepaniec et al., 2011). APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 15(3): 697-711. http://www.aloki.hu ● ISSN 1589 1623 (Print) ● ISSN 1785 0037 (Online) DOI: http://dx.doi.org/10.15666/aeer/1503_697711 2017, ALÖKI Kft., Budapest, Hungary Virić Gašparić et al.: Impact of environment on ground beetles populations - 699 - In this study, the main objectives were to understand how common arable agroecosystems affect ground beetles populations in respect to the environmental conditions. We hypothesized that, within a region, environmental specifics (soil type and structure, climatic conditions) together with cultivation measures (tillage, insecticide application) would affect ground beetle activity and abundance. To test this hypotheses we compared ground beetle abundances and population dynamics in different arable agroecosystems in two different management regions. Materials and methods Sample sites Ground beetles were collected during the arable crop growing season 2015 in two different counties of Croatia representing two distinct climatic and edaphic areas: Lukač (Virovitica – Podravina County) and Tovarnik (Vukovar-Sirmium County). In each county four fields with different cropping history were chosen for ground beetle trapping. The fields were chosen to represent common cultivation and crop rotation practices as well as the agro-technical measures in both areas. Since the soil type and soil characteristics differ between locations, the tillage is adapted to the given conditions. In Virovitica – Podravina County soils contain a great amount of fine sand and coarse silt which requires conservation tillage. This means that autumn ploughing on a depth of 20 – 25 cm is followed by the furrow closure for moisture conservation in spring. In Vukovar – Sirmium County soil contains a great amount of clay which requires deeper autumn mouldboard ploughing (30 – 35 cm). Chisel ploughing and tillage with the rotary harrow in spring and after harvest are usually followed by disk harrowing and again chisel ploughing. Characteristics of sample sites are introduced in Table 1. Climatic and edaphic factors Climate data used in this study (i.e., mean weekly air temperature,